The upside down.
The Study: The authors of this study sought to determine the benefit of PMRT in the context of the OncotypeDX recurrence score (RS) results for women with T1-2N1, ER+ breast cancer between 2004 and 2014 using the NCDB as a discovery cohort and SEER as a validation cohort. Eligible patients could not have received neoadjuvant chemo and had to have had a mastectomy. Only about 10% of the eligible population actually had an RS performed, and that’s where things get complicated because...confounders. First, RS wasn’t even indicated for node positive disease at the time. Second, 20% of patients with low RS got chemo while almost 50% of those with high RS got chemo. Third, only 25-30% of patients in each RS risk group got PMRT. Though PMRT was not associated with improved survival overall, it was associated with a significant 2-3% increase in survival among those with low RS. That’s right, low. The current mantra is that breast cancers with more aggressive biology (i.e. metastatic risk) derive the most benefit from PMRT. The stranger thing is--this data suggests just the opposite.
Bottom Line: T1-2N1, ER+ breast cancer with the lowest risk of distant failure and least benefit from chemo (read: a low RS) may actually derive the greatest benefit from aggressive locoregional therapy with PMRT. | Goodman, Clin Cancer Res 2018